Oven I am returning — beware, bank is involved (9)
I believe the answer is:
microwave
'oven' is the definition.
(I've seen this before)
'i am returning beware bank is involved' is the wordplay.
'i am' becomes 'im'.
'returning' says the letters should be written backwards.
'beware' becomes 'cave' (old-fashioned term meaning 'look out').
'bank' becomes 'row' (I've seen this in other clues).
'is involved' indicates putting letters inside.
'im' written backwards gives 'mi'.
'cave' placed around 'row' is 'crowave'.
'mi'+'crowave'='MICROWAVE'
(Other definitions for microwave that I've seen before include "Cook" , "Modern oven using electromagnetism" , "Fast oven" , "Kind of oven" , "(Kitchen) oven" .)